JP4982510B2 - Video display device - Google Patents

Description

  The present invention relates to a video display device including a display panel, and in particular, in a self-luminous display panel such as a plasma display panel (hereinafter referred to as PDP), a bright video can be displayed while suppressing an increase in power consumption. The present invention relates to a video display device suitable for obtaining.

  Since the PDP display device has a lower total white luminance than a display device using a CRT or LCD, the contrast (bright room contrast) is low in a bright living room in the daytime. In order to increase the display brightness, the number of discharge pulses for driving the display of the PDP and the driving voltage thereof may be increased. However, in this case, there is a problem that power consumption increases.

  As a conventional technique for solving such a problem in the PDP display device, that is, improving the brightness of an image while suppressing power consumption, a process of reducing the luminance at the peripheral portion of the screen below the luminance at the central portion of the screen (hereinafter referred to as such) Such processing is referred to as “shading processing”, and a circuit that performs shading processing is referred to as “shading processing circuit”).

  The shading processing operation will be described with reference to FIG. FIG. 2 shows an example of the reduction rate of the luminance level during the shading processing operation in the case where the display image is the entire white display. FIG. 2A shows the pixel position of the display panel, where X is the horizontal coordinate and Y is the vertical coordinate. In FIG. 2 (b), the vertical axis represents the pixel position in the vertical direction, the horizontal axis represents the ratio to the luminance level of the input video signal after the shading processing operation, and the decrease ratio of the luminance level of the output video signal from the center of the screen to the periphery of the screen. Enlarge.

  In FIG. 2C, the vertical axis represents the ratio to the luminance level of the input video signal after the shading processing operation, and the horizontal axis represents the horizontal pixel position. Similar to FIG. 2B, the screen extends from the screen center to the screen periphery. Increase the reduction rate of the luminance level of the output video signal. Note that the product of the luminance reduction ratios of the X-axis and Y-axis is the actual luminance reduction ratio at the pixel corresponding to each coordinate. As a conventional technique using the above shading processing operation, for example, one described in Patent Document 1 or 2 below is known.

  In the following Patent Document 1 or 2, the shading process uses a human visual characteristic that it is difficult to notice visually even if the luminance at the periphery of the screen is lowered for a bright image with a high luminance level. Such visual characteristics are due to the fact that human vision has a so-called logarithmic characteristic with respect to brightness. The shading process uses an amount of decrease in luminance at the periphery of the screen to increase luminance at the center, so that when displaying a bright image, the visual appearance does not give a sense of incongruity, while reducing power consumption and apparently. It improves the brightness of the image.

Further, as a prior art, a video processing apparatus capable of efficiently controlling the shading processing circuit and suppressing an increase in power consumption and displaying a high-quality video is described in Patent Document 3 below.
This detects the average luminance level of the entire display panel and controls the shading processing operation according to the average luminance level, so that when displaying a bright image (high luminance image), the shading processing circuit is operated and consumed. When a dark video (low luminance video) is input while suppressing an increase in power, the shading processing operation is stopped to prevent image quality deterioration (gradation loss).

JP-A-6-282241 JP 2002-55675 A JP 2005-321664 A

  In Patent Document 3, the shading processing operation is controlled in accordance with the average luminance level of the entire display panel. Therefore, for example, when a video signal in which a low luminance region 10 and a high luminance region 11 are mixed as shown in FIG. 3A is input and the shading process is performed with a high average luminance level as the entire area on the display panel, the low luminance is obtained. Since the shading process is also performed uniformly on the area 10, further reduction in luminance due to shading in the peripheral low-luminance area 10 causes gradation collapse.

Specifically, FIG. 3 (b) and FIG. 3 (c) showing the relationship between the pixel position of the screen peripheral portion 12 and the luminance level in FIG. 3 (a) will be described. When the shading process for lowering the luminance level from the center to the periphery of the screen is operated with respect to the luminance level of the input video in FIG. 3B, the luminance level decreases as shown in FIG. Here, when FIG. 3 (b) and FIG. 3 (c) are compared between X _-4 Y _-4 and X _-3 Y _-4 , which are relatively low-luminance regions, in FIG. Since some luminance levels are below a predetermined threshold, gradation collapse occurs in the periphery of the screen, and the display image becomes black display.

  In an actual display image, there is a high possibility that the above-described image signal (an image in which a bright image and a dark image are mixed) is input, and there is a concern that the image quality deterioration may occur.

  Further, in Patent Document 3 in which the control of the shading processing operation is controlled according to the average luminance level of the entire display panel, for example, the average luminance level of only one color of RGB constituting the pixel is large, and the average luminance of the other colors is When a video signal with a low level is input, the average luminance level of the entire display panel does not reach the threshold value, so the shading process does not operate. Therefore, there is a problem that an increase in power consumption cannot be suppressed.

  The present invention has been made in view of the above problems. The object is to provide a video display device capable of displaying high-quality video while suppressing an increase in power consumption.

  In order to achieve the above object, a video display device according to the present invention is characterized in that a control circuit for controlling a shading processing circuit according to a state quantity relating to the operation of a display panel such as a PDP is provided.

  Specifically, the average luminance level of the input video signal as a state quantity is detected for each display area, and information for reducing the luminance level of the input video from the average luminance level detected for each area (hereinafter referred to as a shading gain coefficient). ) And further determines whether or not the luminance level of the input video signal exceeds a predetermined threshold, and if the luminance level of the input video signal exceeds the predetermined threshold, it is based on the calculated shading gain coefficient. Then, the shading processing circuit is operated. When the shading processing circuit is smaller than the threshold, the operation of the shading processing circuit is stopped.

  According to the present invention, it is possible to display a high-quality video while suppressing power consumption. Specifically, in high-brightness areas where gradation loss does not occur even if the display image is subjected to shading processing, the luminance level of the input image is reduced to suppress an increase in power consumption. In the bright area, the brightness level of the input video is not lowered, thereby preventing the picture quality from being lowered. By these controls, the brightness at the center of the screen is increased without increasing the power consumption, and the bright room contrast is high. Can provide high-quality images.

  Hereinafter, the best mode of the present invention will be described with reference to the drawings. In each figure, parts having the same function are denoted by the same reference numerals, and once described, repeated description is omitted to avoid complication.

  Hereinafter, a PDP display device will be described as an example of a video display device. However, the present invention is not limited to this, and a display panel whose power consumption increases according to a display load, for example, a self-luminous display panel. The present invention can also be applied to a video display apparatus using an LED panel or the like in which a certain field emission display (FED), EL, and LED are provided in a matrix.

  FIG. 5 is a block diagram of a PDP display device showing an embodiment of the present invention. In the figure, it comprises a region-specific average luminance level detection circuit 201, a shading process control signal storage 202, a shading gain coefficient average processing circuit 203, a shading processing circuit 204, a display / drive control circuit 205, and a PDP panel 206.

  The region-specific average luminance level detection circuit 201 and the shading processing control signal storage 202 will be described.

  As shown in FIG. 10, the area-specific average luminance level detection circuit 201 divides the pixels on the display panel into n + 1 divisions in the horizontal direction and m + 1 divisions in the vertical direction, and divides each pixel based on the input video signal. An average luminance level for each of RGB constituting pixels in the region is detected. Then, the maximum value is selected as the average luminance level of each region from among the average luminance levels for each of RGB constituting the pixel, and is output to the shading process control signal storage 202.

  As the output of the average luminance level detection circuit 201 for each region, an average value of average luminance levels for each RGB may be output to the shading process control signal storage 202.

  From the shading processing control signal storage 202, the shading gain coefficient a1 corresponding to the average luminance level selected for each area is shaded as a shading coefficient of pixels corresponding to the four corners of each area (hereinafter referred to as “reference pixels”). It is output to the gain coefficient average processing circuit 203.

Here, the reference pixel will be described with reference to FIG. The reference pixel is set to overlap between a plurality of adjacent regions. For example, (X ₁ , Y ₁ ) in FIG. 6 is located at one of the four corners of each of the regions 1 to 4, and the shading gain of (X ₁ , Y ₁ ) is based on the average luminance level of each region. Four coefficients a1 (X1, Y1) are calculated from the shading process control signal storage 202.

The four shading gain coefficients a1 (X1, Y1) is averaged with the shading gain coefficient averaging circuit 203, a shading processing circuit 204 as (X _1, Y ₁₎ shading gain coefficient a1 '(X _1, Y ₁₎ Is output. Further, the maximum luminance level I _max , the predetermined threshold value I _th and the input video signal are output to the shading processing circuit 204 from the shading processing control signal storage. Here, the predetermined threshold value I _th is a determination value for preventing gradation collapse of the display image, is initially set as a fixed value, and is output to the shading processing circuit 204.

Next, the shading gain coefficient a _{2 at} an arbitrary display coordinate in each area calculated by the shading processing circuit 204 will be described with reference to FIG. The shading gain coefficient a ₂ (P, Q) is calculated by interpolating from the shading gain coefficient a1 ′ of the reference pixel. First, linear interpolation between the two points of the shading gain coefficients a1 ′ (X ₀ , Y ₀ ) and a1 ′ (X ₀ , Y ₁ ) output from the shading gain coefficient average processing circuit 203 (hereinafter, two-point linear interpolation). A ₂ (X ₀ , Q) is calculated. Next, a ₂ (X ₁ , Q) is calculated by two-point linear interpolation between a 1 ′ (X ₁ , Y ₀ ) and a 1 ′ (X ₁ , Y ₁ ), and a ₂ (X ₀ , Q) and _{a 2 (X 1, Q)} a 2 (P, Q) from the point-to-point linear interpolation is calculated. Similarly, the shading gain coefficient corresponding to each pixel in the region is calculated. This is for the purpose of reducing the storage capacity of the shading control signal storage, and shading gain coefficients corresponding to the display coordinates of all input video signals may be stored in the shading control signal storage.

Examples of the shading process control signal hangar 202 shading gain coefficients outputted from a1 and shading processing circuit 204 shading gain coefficient a ₂ calculated in, will be described in FIG. 9 (a). X ₁ Y _{1 to} X ₄ Y ₄ indicate the coordinates of the pixels on the display panel (see FIG. 2). The average luminance level of the calculated input image signal is the larger than the predetermined threshold value I _th is smaller than the shading gain coefficients a1 and a ₂ 1. The shading gain coefficients a1 and a ₂ smaller toward the periphery of the display panel.

Further, when the average luminance level of the calculated input image signal is a predetermined threshold value I _th is smaller than, the value of the shading gain coefficients a1 and a ₂ to 1 (i.e., stops the shading processing).

FIG. 9 (a) but attenuates toward the value I _th ~I _max of the average luminance level of the calculated input video signal shading gain coefficients a1 and a ₂ in the linear, if priority is given to human vision characteristics Further, it may be attenuated nonlinearly as shown in FIG. The value of the shading gain coefficient is an example, and is obtained by multiplying the values of FIG. 2 (b) and FIG. 2 (c).

The arithmetic circuit will be described with reference to FIG. The X axis in FIG. 8 is the luminance level I of the input video signal, and the Y axis is the luminance level O of the output video signal. I _th and O _th are the predetermined threshold values (I _th = O _th ), and when the predetermined threshold value is exceeded, it is desired to reduce the luminance of the input video signal. S becomes smaller. The formula for calculating the slope S of the characteristic 402 is shown in the following equation 1. In addition, the calculation formula of the luminance level O _t of the output video signal after the shading process when the luminance level of the input video signal is larger than the predetermined threshold I _th is shown in the following formula 2. Input luminance level is the output luminance level in the case of I _max and O _G, it shows a calculation formula O _G below equation (3). Thus the maximum input luminance level I _max and the shading gain factor A (hereinafter, the shading gain coefficient used directly for the calculation of the output video signal to A) the O _G calculated from further inclination S using the following expression 1 Then, O _t is determined using Equation 2 below.

また、図８では上記所定の閾値を一種類しか設けていないが、複数の閾値を設けることにより、段階的に出力の輝度レベルを可変してもよい。

In FIG. 8, only one type of the predetermined threshold is provided. However, by providing a plurality of thresholds, the output luminance level may be varied step by step.

In the present application, since the average luminance level for each pixel is the average (R + G + B) / 3 of the average luminance levels for each of RGB constituting the pixel, the first threshold value I _{th1 in} FIGS. 7 (a) and (b). _Is set larger than the second threshold value I _th2 . Accordingly, the inclination S ₁ is smaller than the inclination S ₂ with respect to the inclination. However, the average luminance level for each pixel is not limited to this, and may be the total sum (R + G + B) of the average luminance levels for each of RGB constituting the pixel. In that case, the second threshold value I _th2 is set larger than the first threshold value I _th1 .

  FIG. 1 is a diagram showing an operation processing flow of the embodiment of the present invention shown in FIG. The area-specific average luminance level detection circuit 201 calculates the area-specific average luminance level for each color based on the input video signal (steps 101R, 101G, 101B), and the maximum value among the average luminance levels calculated for each color. Is selected (step 102). Then, the shading gain coefficient a1 is output from the average luminance level selected by the shading control signal storage 202 (step 103), the shading gain coefficient a1 calculated from each region is averaged (step 104), and the shading gain coefficient is calculated. a1 ′ is calculated. This prevents a luminance step at the boundary of the region.

The shading gain coefficient a ₂ calculated by the averaging processed shading gain coefficients a1 'and interpolated input to the shading processing circuit 204. In the determination circuit in the shading processing circuit 204, when the maximum luminance level for each color of the input video signal is larger than the first threshold, the shading gain coefficient a1 calculated for each corresponding pixel as the shading gain coefficient A in step 107. , a1 ', to select a ₂ or the like. If the maximum luminance level for each color is smaller than the first threshold value, the luminance level of one pixel is determined in step 106, and if it is larger than the second threshold value, the shading gain coefficient A in step 107 is determined for each corresponding pixel. calculated shading gain coefficients a1 ', select a _2, it is smaller than the second threshold value, and outputs 1 as the shading gain coefficient a in step 108 to the arithmetic circuit. The first threshold value and the second threshold value may be the same.

As described above, according to the present embodiment, even when a video signal as shown in FIG. 4 (a) is input, as shown in FIG. 4 (c), the low luminance region 10, that is, X ₄ Y ₄ and X _It is possible to control the shading processing operation between ₄ Y ₃ and prevent image quality deterioration due to gradation loss in a low luminance region. 4A and 4B are the same as FIGS. 3A and 3B, respectively.

  On the other hand, the average luminance level of only one color of RGB constituting the pixels of each region is large, but the shading process can be operated even when an input video signal having a low average luminance level is input as a whole on the display panel. Therefore, it is possible to provide high-quality images with good contrast by increasing the luminance at the center of the screen without increasing power consumption.

  In this embodiment, the PDP is described as an example of the self-luminous display panel. However, the present invention can be similarly applied to FED, EL, and LED as described above. Further, the present invention can be similarly applied to a non-self-emitting type such as an LCD.

  The present invention can be used for a video display device using a PDP display panel or the like.

It is a figure which shows the processing flow of the Example by this invention. It is a figure explaining a shading process. It is a figure explaining the subject at the time of the shading process operation | movement in a prior art. It is a figure explaining the effect at the time of the shading process operation | movement in this invention. It is a block diagram of a PDP display device showing an embodiment of the present invention. It is a figure explaining the shading coefficient average processing circuit in this invention. It is a figure explaining the selection method of the shading gain coefficient in arbitrary display locations. It is a characteristic view of the luminance level after the shading process based on an Example. FIG. 6 is a characteristic diagram of a shading gain coefficient a according to an embodiment. It is the figure which subdivided the detection area of the average luminance level.

  DESCRIPTION OF SYMBOLS 201 ... Average brightness level detection circuit classified by area, 202 ... Shading process control signal storage, 203 ... Shading gain coefficient average processing circuit, 204 ... Shading processing circuit, 205 ... Display / drive control circuit, 206 ... PDP panel.

Claims (3)

A video display device that performs a shading process for reducing the display luminance level of the peripheral portion on the display panel with respect to the luminance level of an input image signal,
An area-specific average luminance level detection circuit for detecting an average luminance level for each area by dividing the display area of the display panel into a plurality of areas in both the horizontal direction and the vertical direction;
A shading processing circuit that changes a shading gain coefficient, which is a ratio of reducing the luminance level on the display panel of the image signal to be displayed, according to the average luminance level for each region detected by the region-specific average luminance level detection circuit. And
The average luminance level for each region is a maximum value among the average luminance levels for each color constituting the pixels in the region, and the average luminance level of the region,
The shading processing circuit stops the shading process by setting the shading gain coefficient to 1 in an area where the average luminance level for each area is equal to or less than a predetermined threshold, and the average luminance level for each area is larger than the predetermined threshold. In this case, the shading gain coefficient is gradually decreased as it increases ,
A shading gain coefficient of a reference pixel corresponding to pixels at the four corners of the area is calculated by averaging the shading gain coefficient according to an average luminance level for each area in the area including the reference pixel,
A video display device , wherein a shading gain coefficient of each pixel other than the reference pixel included in the region is calculated by an interpolation process based on the shading gain coefficient of a plurality of the reference pixels . The video display device according to claim 1,
The video display device , wherein the shading gain coefficient of each pixel other than the reference pixel included in the region is calculated by linear interpolation processing of the shading gain coefficients of a plurality of the reference pixels . A video display device according to any one of claims 1 to 2 ,
A value obtained by averaging the average luminance level for each color constituting the pixels in the region is set as a second average luminance level for each region,
The shading processing circuit performs the shading processing without setting the shading gain coefficient to 1 in the region where the second average luminance level is larger than a second threshold smaller than the predetermined threshold. A video display device characterized by that.

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